The World Health Organization (WHO) said on Tuesday it had delivered life-saving medical supplies to the southern city of Aden in Yemen, where most health facilities are "non-functional" due to fighting and critical shortages of supplies.

In a statement, the WHO said it had brought 46.4 tonnes of assistance including trauma kits, medicines for treating malaria and diarrhoeal diseases, and water and sanitation supplies for more than 84,000 people in six trucks as part of a United Nations convoy.

"Access to health care in Aden is extremely limited due to constant fighting and most of the governorate's 31 health facilities are non-functional due to critical shortages in medical supplies and fuel needed for generators," it said.

Humanitarian pause failing

More than 3,000 people have been killed and over a million displaced in a conflict between Shi'ite Houthis and forces loyal to President Abd-Rabbu Mansour Hadi, who has fled to Riyadh. The United Nations says 21 million people need help, about 80 percent of the population.

Johannes Van Der Klaauw, the U.N. resident coordinator for Yemen, said that the U.N. convoy arrived in Aden at the weekend, but that rations supplied by the World Food Programme (WFP) aboard several dozen trucks had been delayed.

"It took days and days to organise safe passage. It did arrive in Aden last Saturday. It was the first time we got a convoy into Aden for weeks," Van Der Klaauw told reporters in Geneva.

U.N. Secretary-General Ban Ki-moon is "very much disappointed" that a U.N.-brokered humanitarian pause in fighting in Yemen did not take hold over the weekend, his spokesman said on Monday.

"We had wanted to use ports, vessels which try to dock in Aden. But since the pause didn't take place, we still have a big problem that aid is not reachable by sea," Van Der Klaauw said, adding that vessels are diverted to Hodeida port.